notes

A folk etymology goes that "my bad" was originally "my bag", and that the latter is from the card game Spades.

Here is one such submission:

My Bad was originally My Bag. It was common as far back as the 1940s and into 80s. The origin of this phrase actually comes from the card game Spades. The player that predicted wrong would say to his partner my bag meaning my fault. Spades originated in the Midwestern United States in the late 1930s. It was invented by college students who enjoyed both Whist and Bridge. The game really took off during WWII. It spread to factories and offices all across the country. Today there are clubs and tournaments and it's popular on the internet.